Process for the Preparation of a 1,3-Butadiene and Styrene Copolymer Containing a Random Section in its Main Chain Followed by a Block with a Structure Differentiated from the Main Chain, Homopolymeric or Copolymeric, Functionalized and the Product Obtained From This

ABSTRACT

This invention refers to a process for the preparation of a 1,3-butadiene and styrene copolymer, containing a random section in its main chain, followed by a block with a structure differentiated from the main chain, homopolymeric or copolymeric, functionalized, and the product obtained from this.

This invention refers to a process for the preparation of a1,3-butadiene and styrene copolymer, containing a random section in itsmain chain, followed by a block with a structure differentiated from themain chain, homopolymeric or copolymeric, functionalized, and theproduct obtained from this.

BACKGROUND OF THE INVENTION

Obtaining materials that are perfectly adaptable in their usage has beena constant challenge for science and technology in recent years. Thegrowing demand for materials that have an appropriate balance ofimportant and specific properties, added to the ecological restrictionsof utilization, has produced great efforts from scientists in the searchfor innovative solutions to these challenges.

The science of polymers has made a decisive contribution to thisprocess. Due to intensive research and the use of sophisticatedprocesses of polymerization, new products have been obtained, with acombination of properties that until now were not found in traditionallyknown materials. The emphasis with respect to the environment has guidedthis research and generated processes and products that are increasinglyecologically appropriate.

Among the wide variety of polymers, the elastomers are the best known.Due to their large capacity to deform elastically when submitted totension and then return spontaneously to their original form when thetension ceases, elastomers can be employed to obtain many importantproducts when correctly used in the form of vulcanized compounds. Amongthese products are mainly tires, in all their complexity, includingtheir constituents such as the tread, sidewalls etc, as well as mats,straps and a wide range of technical products.

These rubber or elastomeric products, in determinate applications, needto present a series of properties, which cannot always be combinedsimultaneously. In the case of tires for automobiles, the followingproperties are required; elasticity, low abrasion wear, good adhesion ondifferent surfaces, and wet skid resistance, in low and hightemperatures. Performance improvement in one of these propertiesnormally results in a decrease in the performance in one of the others.This is equally undesirable and most of the time it becomes impossibleto optimize all the properties.

A number of solutions have been used by tire manufacturers, with theobjective of combining and improving the different properties of theirproducts. This has, essentially consisted in the combined use ofdifferent elastomers in the utilization of different reinforcementloads, which interact physically and chemically with the elastomers, andin the use of compatible additives in the preparation of the vulcanizedrubber compounds.

For example, tires manufactured with elastomers of the type SBR(copolymers 1,3-butadiene-styrene), including those produced in a coldemulsion (E-SBR) and those produced in a solution (S-SBR), with achemical content of combined styrene of approximately 23%, present ahigh wet skid resistance, and also a high rolling resistance. The tiresthat are manufactured with conventional elastomers such as the 1,4-CisBR (polybutadiene High Cis), NR (Natural Rubber) and IR (Polyisoprene),present low rolling resistance and low wet skid resistance (P. L. A.Coutinho, C. H. Lira, L. F. Nicolini, A Ferreira; Elastomers for the“Green Tire”, 1^(st) Chemical and Petrochemical Industry Congress ofMercosur, Buenos Aires, Argentina, 1998). The appropriate combination ofthese different elastomers, in vulcanized compounds, allows theproduction of tires with an improved balance of properties.

Moreover, the use of compatible additives, utilized in the preparationof vulcanized compounds, or even the employment of modified elastomersin the polymeric structure, including the incorporation of specificfunctional groups, increases the miscibility between the differentelastomers, as well as their interaction with the reinforcement loads,which markedly improves the resulting properties of the tire.

As has been described in other researches, an increase in the chemicalcontent of the 1,2-vinylic units, in the polydienic sections of theelastomers of type S-SBR, results in an increase of its glass transitiontemperature Tg), which provides an improvement in the skid resistanceproperties of the vulcanized compounds for tires. (C. H. Lira, L. F.Nicolini, G. Weinberg, N. M. T. Pires, P. L. A. Coutinho—Elastomers ForHigh Performance Tires—Presented at a Meeting of the Rubber Division,American Chemical Society, Cleveland, Paper N° 112, 2001).

Moreover, it was demonstrated that a higher chemical content of theseunits assists the solubility of the elastomers of type S-SBR in otherelastomers, such as 1,4 Cis-BR and NR(R. H. Schuster, H. M. Issel and V.Peterseim—Selective Interactions in Elastomers; A Base for Compatibilityand Polymer-Filler Interactions; Rubber Chem. Technol., 69, 5, 1996).

Therefore, any structural modification that can be incorporated into thedifferent elastomers that assists the miscibility between them, besidesproviding an improved compatibility with the different reinforcementfillers employed in the vulcanized elastomeric compounds, also improvesthe resulting properties of the tires.

There is a special interest in the tread, the part of the tire where themain mechanical forces are concentrated and where the properties withrespect to safety, such as wet/icy skid resistance, are demanded.

The elastomeric compounds used in the production of tires, especially inthe tread, are normally composed of copolymers, formed by a conjugateddiene and a monomer with an aromatic vinyl structure.

Elastomers of type S-SBR are mainly used. These copolymers present apredominantly random distribution of their constituent mers along theirpolymeric chains and can also present sections with blockeddistribution, or a mixture of random and blocked distribution. They aredecisive in the obtainment of the final properties of the tire. Thefollowing material deals with the current state of the art and isincorporated in its entirety as a reference.

As has been previously stated, the state of the art with respect totires, especially the tread, requires a level of development that allowsthe employment of new materials, or rather polymers, which provide tires(and the tread) with a high performance, in view of given vehicle andtire performance conditions.

In the documentation of patent EP 0929582 (U.S. Pat. No. 6,013,718) andEP 1110998 (U.S. Pat. No. 6,667,362 B2), there is a description of thepreparation and use of polydienes and copolymers resulting in thecopolymerization between the conjugated dienes and a monomer with anaromatic vinyl structure (e.g.: S-SBR), which contains functional groupsof siloxane and silanol in the end section of the polymeric chains.These groups interact with the silica used in the vulcanized compounds,improving its properties. The patents display the comparative resultsobtained from the employment of these elastomers in several vulcanizedelastomeric compounds.

The patent GB 2368069 describes the process of the preparation of thefunctionalized polymers in both the extremities of the polymeric chains.Its structure is essentially that of a triblock, where the intermediarysection can be a polydiene or a copolymer, resulting from thecopolymerization between the conjugated diene and a monomer with anaromatic vinyl structure (e.g.: S-SBR), where the end sections arepreferentially polydialkylsiloxanes.

The patent EP 0849 333 B2 describes the use of siloxanes substituted inthe preparation of the polydienes or copolymers, resulting from thecopolymerization between the conjugated dienes and a monomer with anaromatic vinyl structure. The use of these functionalized polymers invulcanized elastomeric compounds and their observed properties are alsopresented.

In view of the abovementioned state of the art developments, thisinvention provides a product and a process of preparation of a newfamily of elastomers of type S-SBR, designed principally for theproduction of high performance tires. The production of these elastomersuses advanced processes of polymerization, allowing larger control overthe macrostructure and microstructure of the polymer.

The elastomeric product thus produced allows for the production of tireswith highly desirable performance specifications, particularly withrespect to the tread.

OBJECTIVE OF THE INVENTION

The objective of this invention is the preparation of elastomers of typeS-SBR (copolymers of 1,3-butadiene-styrene), modified, in theirpolymeric structure and functionalized at the extremity, and thepreparation process.

More specifically, this invention deals with the preparation ofcopolymers of type S-SBR, with a controlled macrostructure andmicrostructure, the introduction of blocks with one or more monomers atthe end of the polymeric chains, followed by a terminalfunctionalization, and the employment of these copolymers in vulcanizedelastomeric compounds and their properties.

DESCRIPTION OF THE INVENTION

This invention refers to a process for the preparation of a1,3-butadiene and styrene copolymer containing a random section in itsmain chain, followed by a block with a structure differentiated from themain chain, homopolymeric or copolymeric, functionalized, and a productthat includes a 1,3-butadiene and styrene copolymer, with a randomsection in the main chain, followed by a block with a structuredifferentiated from the main chain, homopolymeric or copolymeric,functionalized. More particularly, this invention provides new polymericmaterials of 1,3-butadiene and styrene. This allows for the manufactureof tires and tread with highly desirable characteristics andperformance.

The total control over the polymeric architecture results in elastomerswith an improved balance of mechanical properties and therefore greatersuitability to their end use.

Although it is known that polydienes and/or copolymers, resulting fromthe copolymerization between conjugated dienes and a monomer with anaromatic vinyl structure, can be functionalized in their extremities, inthe appropriate conditions, bringing benefits to their employment invulcanized elastomeric compounds, the effect of a structural change inthe polymeric chains of these polymers, which includes a smallhomopolymeric or copolymeric block, situated in one or both of theextremities of the polymeric chains, followed by terminal functionalgroups, in the properties of the vulcanized elastomeric compounds, isnot known in the state of the art.

Also, the effect of these blocks, formed by homopolymers or copolymers,which have different glass transition temperatures (Tg) from the mainchains of the elastomer, in the properties of the vulcanized elastomericcompounds, is not known.

It is not known that the wet/icy skid resistance properties ofvulcanized elastomeric compounds can be improved by using in theirpreparation an elastomer, which includes a small homopolymeric orcopolymeric block, situated in one or both of the extremities of thepolymeric chains, followed by terminal functional groups.

The Product

The elastomers in this invention are copolymers of the functionalizedtype S-SBR, produced by the process of anionic polymerization insolution.

They are basically formed by a preferential composition between one ormore conjugated dienes and one or more monomers with an aromatic vinylstructure, in appropriate proportions. They have a controlledmacrostructure and microstructure, with an appropriate chemical contentof 1,2-vinylic units, based on the conjugated diene incorporated in thecopolymer, and the specific functional groups in the polymericstructure.

These elastomers have a predominantly random distribution of theirconstituent mers, along the main polymeric chains. At the end of thesechains, in one or both of the extremities, is a small block, with astructure differentiated from the main chain, which can be homopolymericor copolymeric. Beyond the small blocks at the end of the chains, theseelastomers have a terminal functionalization, preferentially withfunctional functionalization with specific functional groups, whichinteract and/or react with the reinforcements of the vulcanizedcompounds.

The small polymeric blocks with the differentiated structure, situatedat the end of the polymeric chains, can have different lengths,preferentially between 5 and 250 mers and more preferentially between 20and 180 mers. The 1,4-cis, 1,4-trans, 1,2-vinyl and even the 3,4-vinylunits can also be present in the structure, depending on the conjugateddiene employed.

The terminal functional groups of the polymeric chains of theseelastomers are preferentially of the type —OH, —COOH, —COX, where X is ahalogen, —SH, —CSSH, —NCO, amine, epoxy, silyl, silanol or siloxane, aswell as the polysiloxane groups, and siloxanes or polysiloxanescontaining amine groups.

Preferentially, these groups can be better represented by the followingstructures:

Amine groups: —N(R₁)₂, —NR₁R₂, —NHR₁, —NH₂, where R₁ and R₂ areidentical or different, can be alkyl, linear or branched, cycloalkyl,aryl, alkylaryl, aralkyl or vinyl groups, in each case having 1 to 20carbon atoms;

Silyl, silanol and siloxane groups: —SiH₂(OH), —Si(R₁)₂(OH),—SiH(OH)₂,—SiR₁(OH)₂, —Si(OH)₃, —Si(OR₁)₃, —(SiR₁R₂O)_(x)—R₃, —Si(R₃)₃,(X)_(m), where X is a halogen, x is the number of repetitive unitsbetween 1 and 500, m is the number of linked groups, varying from 0 to3, R₁ and R₂ are identical or different, and can be alkoxy or alkyl,linear or branched, cycloalkyl, aryl, alkylaryl, aralkyl or vinylgroups, in each case having 1 to 20 carbon atoms, and R₃ is H or alkyl,linear or branched, in each case having 1 to 20 carbon atoms, or amononuclear aryl group;

Siloxane groups that contained amine groups, are represented by theformula—A¹-Si(A²-N((H)_(k)(R₁)_(2-k)))_(y)(OR₁)_(z)(R₃)_(3-(y+z)),where: k can vary from 0 to 2, y can vary from 1 to 3, and z can varyfrom 0 to 2, 0≦y+z≦3, being that R₁ and R₂ are identical or different,and can be alkyl, linear or branched, cycloalkyl, aryl, alkylaryl,aralkyl or vinyl groups, in each case having 1 to 20 carbon atoms,mononuclear aryl groups, R₃ is H or alkyl, linear or branched, in eachcase having 1 to 20 carbon atoms, or a groups that interact and/or reactwith the reinforcements utilized in the vulcanized elastomeric compounds

Furthermore, the main chains are linear or branched, with a controlledmicrostructure, and present a determinate content of 1,2-vinylic units,based on the conjugated diene incorporated in the copolymer.

Elastomers with radial polymeric chains, or even a mixture of linear andradial chains, can also be obtained in the appropriate conditions. Forthis to happen, it is necessary to use coupling agents, such as tin,tetrachloride (SnCl₄) and silicon tetrachloride (SiCl₄), with rigorouscontrol over the efficiency of the coupling reactions.

More specifically, these elastomers are copolymers obtained by thepolymerization of one or more monomers of the conjugated diene type(e.g.: 1,3-butadiene) with one or more monomers with an aromatic vinylstructure (e.g.: styrene), which present a predominantly randomdistribution of their constituent mers in the main chain, whereinmicrosequences of a same mer have preferentially less than 10 units, andhas a preferentially linear or branched structure. They also present acontrolled microstructure, with a chemical content of 1,2-vinylic unitsbetween 8% and 80%, based on the total of the conjugated dieneincorporated in the copolymer, and can also present different content of1,4-cis, and 1,4-trans units, as well as 3,4-vinyl, depending on theconjugated diene employed.

These elastomers present, at one extremity or both extremities of theirpolymeric chains, a small block with a structure differentiated from themain chain, homopolymeric (e.g.: polybutadiene or polystyrene) orcopolymeric, (e.g.: the copolymerization of two or more conjugateddienes, or the copolymerization of two or more monomers with an aromaticvinyl structure, or the copolymerization of one or more conjugateddienes with one or more monomers with an aromatic vinyl structure,including the possible different microstructures for the employeddiene(s), provided that the final structure of this block is differentfrom the main chain, followed by a terminal mononuclear aryl group, andA¹ and A² are chains of up to 12 carbon atoms, linear or branched,preferentially alkyl, alyl or vinyl.

For the elastomers of this invention, siloxanes are preferentially used,as terminal functional groups of their polymeric chains, in the form ofstructures that can be represented by the generalformula—[—Si(R₁R₂)—O—]_(n)—Si(R₁R₂)—OH, where R₁ and R₂ are identical ordifferent, and can be alkoxy or alkyl, linear or branched, cycloalkyl,aryl, alkylaryl, aralkyl or vinyl groups, in each case having 1 to 20carbon atoms, and n represents the number of units of the siloxanefunctional group before a silanol terminal group, varying from 1 to 500.

Polysiloxane sequences or blocks can also be incorporated anddistributed along the polymeric chains although they are preferentiallyterminal.

Small sequences or microsequences of one of the monomers of thecopolymer, situated along the polymeric chains, can also form part ofthe structure of these elastomers.

More specifically, the elastomers of this invention present a percentagecomposition in weight of their main chain, which can vary from 5% to50%, for the aromatic vinyl monomer (e.g.: styrene), and from 50% to 95%for the conjugated diene (e.g.: 1,3-butadiene). Preferentially, theseelastomers present a composition from 15% to 40% for the % w/w of themonomer with an aromatic vinyl structure, and from 70% 60% to 85% forthe % w/w of the conjugated diene incorporated in the copolymer.

They have a controlled microstructure, with a chemical content of1,2-vinylic units from 8% to 80%, in the main chain, based on theconjugated diene incorporated in the copolymer. More preferentially, thechemical content of the 1,2-vinylic units found in the range from 10% to70%, can also present different chemical contents in its microstructureof 1,4-cis, and 1,4-trans units, as well as 3,4-vinyl units, dependingon the conjugated diene employed in the copolymerization.

These elastomers present at the end of their polymeric chains, at one orboth of the extremities, a small block with a structure differentiatedfrom the main chain, homopolymeric (e.g.: polybutadiene or polystyrene)or copolymeric, e.g.: copolymerization of two or more conjugated dienes,or copolymerization of two or more monomers with an aromatic vinylstructure, or copolymerization of one or more conjugated dienes with oneor more monomers with an aromatic vinyl structure, including thepossible different microstructures for the diene(s) employed providedthe end structure of this block is different from the main chain.Preferentially, these small blocks at the end of the polymeric chainsconsist of polybutadiene or polystyrene, followed by a terminalfunctionalization with the siloxane and silanol functional groups.

To obtain this functionalization in the extremities of the polymericchains, the following are used preferentially;hexamethylcyclotrisiloxane (D₃), which allows the incorporation ofcontinuous sequences of the siloxane functional group —[—Si(CH₃)₂—O—]—,with different lengths, and a silanol terminal group —Si(CH₃)₂—OH.

These elastomers have a Mooney Viscosity (Ml1+4 @ 100° C.) in a rangefrom 30 to 90, and an average molecular weight in the range fromMw=80,000 to 700,000, with a polydispersion in the range from 1.05 to4.0, when analyzed by Size Exclusion Chromatography (SEC), based onpolystyrene standards.

These elastomers present glass transition temperatures, Tg, in the rangefrom −92° C. to −1° C., depending on the chemical content of thearomatic vinyl monomer of the copolymer and the microstructure of theconjugated diene incorporated in the copolymer.

They present, in one or both extremities of their polymeric chains, asmall block with a polymeric structure differentiated from the mainchain. This block can be homopolymeric (e.g.: polybutadiene orpolystyrene) or copolymeric, (e.g.: copolymerization of two or moreconjugated dienes, or copolymerization of two or more monomers with anaromatic vinyl structure, or copolymerization of one or more conjugateddienes with one or more monomers with an aromatic vinyl structure,including the different microstructures possible for the diene(s)employed, provided that the final structure of this block is differentfrom the main chain. These small blocks contain from 5 to 250incorporated mers per chain. It is preferable that these blocks containfrom 10 to 200 incorporated mers and, even more preferable that theycontain from 20 to 180 incorporated mers per chain.

The elastomers of this invention also have a terminal functionalization,which is based on the preferential incorporation of a sequence ofsiloxane groups —[—Si(CH₃)₂—O—]—, which vary in the range from 1 to 500units per polymeric chain, followed by the silanol termination(—Si(CH₃)₂—OH).

A schematic representation of the structures of these elastomers ispresented below.

where, A represent the main chains of a polymer, formed by thecopolymerization between one or more conjugated dienes with one or moremonomers with an aromatic vinyl structure (e.g.: S-SBR), which have apreferentially random distribution of their constituent mers, linear orbranched structure, and a controlled chemical content of 1,2-vinylicunits, based on the incorporated conjugated diene;B represents a block with a structure differentiated from the mainchain, homopolymeric (e.g.: polybutadiene or polystyrene) orcopolymeric, (e.g.: copolymerization of two or more conjugated dienes,or copolymerization of two or more monomers with an aromatic vinylstructure, or copolymerization of one or more conjugated dienes with oneor more monomers with an aromatic vinyl structure, including thedifferent possible microstructures for the diene(s) employed, providedthat the final structure of this block is different from the main chain;

F is terminal functional groups of the polymeric chains of theseelastomers preferentially of the type —OH, —COOH, —COX, where X is ahalogen, —SH, —CSSH, —NCO, amine, epoxy, silyl, silanol or siloxane, aswell as the polysiloxane groups, and siloxanes or polysiloxanescontaining amine groups; and preferentially:

-   -   Amine groups: —N(R₁)₂, —NR1R2 —NHR₁, —NH₂, where R₁ and R2 are        identical or different, can be alkyl, linear or branched,        cycloalkyl, aryl, alkylaryl, aralkyl or vinyl groups, in each        case having 1 to 20 carbon atoms;    -   Silyl, silanol and siloxane groups: —SiH₂(OH), —Si(R₁)₂(OH),        —SiH(OH)₂, —SiR₁(OH)₂, —Si(OH)₃, —Si(OR₁)₃, —(SiR₁R₂O)_(x)—R₃,        —Si(R₃)_(3-m)(X)_(m), where X is a halogen, x is the number of        repetitive units between 1 and 500, m is the number of linked        groups, varying from 0 to 3, R₁ and R₂ are identical or        different, and can be alkoxy or alkyl, linear or branched,        cycloalkyl, aryl, alkylaryl, aralkyl or vinyl groups, in each        case having 1 to 20 carbon atoms, and R₃ is H or alkyl, linear        or branched, in each case having 1 to 20 carbon atoms, or a        mononuclear aryl group;    -   Siloxane groups that contained amine groups, are represented by        the formula        -A¹-Si(A²-N((H)_(k)(R₁)_(2-k)))_(y)(OR₁)_(z)(R₃)_(3-(y+z)),        where: k can vary from 0 to 2, y can vary from 1 to 3, z can        vary from 0 to 2, 0≦y+z≦3, being that R₁ and R₂ are identical or        different, and can be alkyl, linear or branched, cycloalkyl,        aryl, alkylaryl, aralkyl or vinyl groups, in each case having 1        to 20 carbon atoms, mononuclear aryl groups, R₃ is H or alkyl,        linear or branched, in each case having 1 to 20 carbon atoms, or        a mononuclear aryl group, and A¹ and A² are chains of up to 12        carbon atoms, linear or branched, preferentially alkyl, alyl or        vinyl.

Examples of these elastomers, with their main characteristics, arepresented in Table 1 (group 1 of elastomers) and in Table 2 (group 2 ofelastomers), as follows, including the applicable ranges for each item:

TABLE 1 Group 1 of elastomers Applicable S-SBR B1 S-SBR B2 RangeStyrene/Butadiene 19.0/81.0 19.6/80.4 5/95 to 50/150 ratio(main chain)by weight, % Content of the 1,2-   64.1   63.7 8 to 80 Vinylic Units, %^((a)) Mooney Viscosity   60.9   58.3 30 to 90 (Ml 1 + 4 @ 100° C.)Molecular Weight and Mw = 412,000 Mw = 432,000 80,000 to PolydispersionPd = 1.2 Pd = 1.3 700,000 (SEC, PS standards) Pd = 1.05-4.0 GlassTransition −25.4 −25.5 −92 to −1 1 Temperature, Tg, DSC, ° C. Structureof the main Statistical Copolymer Statistical Copolymer Micro-sequenceselastomer chain 1,3-butadiene-styrene; 1,3-butadiene-styrene; of a samemer RMN¹H linear chains linear chains which has less than 10 unitiesunits Block with mers of Block with an average Block with an average of5 to 250 butadiene at the end of of 50 mers of butadiene 150 mers ofbutadiene per the main chain per chain, followed by chain, followed byfunctionalization functionalization Functionalization Terminal with anTerminal with an average 1 to 500 —[—Si(CH₃)₂—O—]_(n)—Si(CH₃)₂—OHaverage of 8.0 groups of 5.0 groups per chain per chain including theincluding the silanol silanol group group DSC = Differential ScanningCalorimetry. SEC = Size Exclusion Chromatography PS = polystyrene ^((a))= based on the content of the diene incorporated in the copolymer

TABLE 2 Group 2 of elastomers Applicable S-SBR C1 S-SBR C2 RangeStyrene/Butadiene 21.4/78.6 23.3/76.7 5/95 to 50/150 ratio (main chain)by weight, % Content of the 1,2-   62.8   61.0 8 to 80 Vinylic Units, %^((a)) Mooney Viscosity   56.4   54.9 30 to 90 (Ml 1 + 4 @ 100° C.)Molecular Weight and Mw = 352,000 Mw = 358,000 80,000 to PolydispersionPd = 1.34 Pd = 1.4 700,000 (SEC, Pd = 1.05-4.0 PS standards) GlassTransition −24.7 −19.3 −92 to 1 Temperature, Tg, DSC, ° C. Structure ofthe main Statistical Copolymer Statistical Copolymer Micro-sequenceschain 1,3-butadiene-styrene; 1,3-butadiene-styrene; of a same mer RMN¹Hlinear chains linear chains which has less than 10 unities Block withmers of Block with an average of Block with an average 5 to 250 styreneat the end of 54 mers of styrene per of 130 mers of styrene the mainchain chain, followed by per chain, followed by functionalizationfunctionalization Functionalization Terminal with an average Terminalwith an 1 to 500 —[—Si(CH₃)₂—O—[_(n)—Si(CH₃)₂—OH of 3.0 groups per chainaverage of 3.0 groups including the silanol per chain including groupthe silanol group DSC = Differential Scanning Calorimetry. SEC = SizeExclusion Chromatography PS = polystyrene ^((a)) = based on the contentof the diene incorporated in the copolymer

The Production Process

For the production of these elastomers, it is necessary to employ apolymerization process that allows a refined control over the polymericstructure of the final product.

The anionic polymerization and its characteristic of “livepolymerization”, allows the obtainment of polymers with a controlledarchitecture. Due to their large versatility, varied polymericstructures can be obtained, allowing a large control over themicrostructure and the macrostructure of the polymer, including theincorporation of functional groups in the polymeric chains.

The process requires a rigorous inspection of the employed materials toremove any impurities that could act as terminators and/or prejudice thecontrol of the polymerization.

The elastomers cited in this invention are obtained by this process ofpolymerization, with the employment of different rectional conditionsand additives that aim to incorporate determinate characteristics in thefinal product.

The process of polymerization of these elastomers can be conducted in acontinuous manner or in batches. However, the batch process is normallypreferred because it provides a better control over the variables thataffect the molecular architecture of the polymer.

The reactions of the polymerization, strictly speaking, are realizedemploying solvents, preferentially apolar, such as cyclohexane orn-hexane, although other solvents of the aliphatic class can also beutilized. Solvents of the aromatic class, such as toluene, can also beemployed. However, their use is to be avoided because it negativelyaffects the kinetics of the reactions, is more difficult to remove, andfor environmental restrictions.

The initiator normally employed in these polymerizations isn-butyl-lithium although, in general, compounds of the group ofalkyl-lithiums can also be employed. Examples of the alkyl groups ofthese initiators are: methyl, ethyl, n-propyl, isopropyl, n-butyl,sec-butyl, t-butyl, n-amyl, sec-amyl, n-hexyl, sec-hexyl, n-heptyl,n-octyl, n-nonyl, n-dodecyl and octadecyl.

More specifically, the initiators are: n-butyl-lithium,sec-butyl-lithium, n-propyl-lithium, isobutyl-lithium, t-butyl-lithiumand amyl-lithium.

Alkyl-dilithium or even alkyl-multi-lithium initiators, as described inthe patents WO 02/02063 and GB 2368069, can also be utilized for theobtainment of these elastomers.

The monomers 1,3-butadiene and styrene are mainly used for theproduction of these elastomers, although other conjugated dienes andother vinyl-aromatic monomers can also be employed.

Of the conjugated dienes, aside from 1,3-butadiene, there are:2-alkyl-1,3-butadiene, 2,3-dialkyl-1,3-butadiene,2-alkyl-3-alkyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene,2,4-hexadiene, etc. As well as styrene, other vinyl-aromatic monomerscan also be employed, such as alpha-methyl-styrene, orto, meta and paradivinylbenzene, orto, meta and para-methylstyrene, para-t-butyl-styrene,vinyl-toluene, methoxystyrene, vinylmesitylene, etc.

For the control of the chemical content of the 1,2-vinylic units of thediene incorporated in the copolymer, polar substances are utilized thatact as Lewis bases, such as N,N,N′,N′-tetramethylethylenediamine(TMEDA), tetrahydrofurane (THF) or ditetrahydrofurylpropane (DTHFP). Awide range of ethers and amines can also be utilized, for example:dimethyl ether, diethyl ether, di-n-propyl ether, diisopropyl ether,di-n-butyl ether, dioxane, ethylene glycol dimethyl ether, ethyleneglycol diethyl ether, diethylene glycol dimethyl ether, diethyleneglycol diethyl ether, triethylene glycol dimethyl ether, trimethylamine, triethyl amine, N-methyl morpholine, N-ethyl morpholine, N-phenylmorpholine, etc.

The terminal functionalization of these elastomers is introduced withthe objective of improving the interaction of the polymeric chains withthe reinforcements in the vulcanized compounds. It is usually introducedutilizing a functionalized terminator, or by the reaction between theactive terminals of the polymeric chains and the compounds that presentdesirable functional groups.

A large variety of functionalizations can, in principle, be incorporatedin these elastomers. It is preferable that these functionalizations areincorporated in at least one of the extremities of the polymeric chains,or in both.

For example, a functional group can be introduced via the utilization ofa functionalized initiator, and the other by the utilization of aterminator, also functionalized, at the end of the polymeric chains. Thegroups can be identical or different.

It is preferable that the functional groups are directly linked to thesmall polymeric block with a differentiated structure, instead of beinglinked to the part of the polymeric chain that has a random distributionof mers (main chain), since in this position the interaction and/orreaction with the reinforcements is favorable.

It is also preferable that the small polymeric block with adifferentiated structure remains in close proximity to this region ofthe interaction between the reinforcements and the functional groups,that is, preferentially at the end of the polymeric chains.

It is known that a large variety of compounds can be utilized for thefunctionalization of polymers, such as ethylene oxide, benzophenone,carbon dioxide, dialkylaminobenzaldehyde, carbon disulfide,alkoxysilanes, alkylphenoxysilanes, phenoxysilanes, etc.

The patents EP 396780 and EP 849333 provide examples of compounds andprocesses that can be employed with this objective. These patents areincluded in this document for reference.

The terminal functional groups of the polymeric chains of theseelastomers, are preferentially of type —OH, —COOH, —COX, where X is ahalogen, —SH, —CSSH, —NCO, amine, epoxy, silyl, silanol or siloxane, aswell as the polysiloxane and siloxane groups or polysiloxane containingamine groups.

Some of these groups can be better represented by the followingstructures:

-   -   Amine groups: —N(R₁)₂, —NR1R2-NHR₁, —NH₂, where R₁ and R2 are        identical or different, can be alkyl groups, linear or branched,        cycloalkyl, aryl, alkylaryl, aralkyl or vinyl, in each case        having from 1 to 20 carbon atoms;    -   Silyl, silanol and siloxane groups: —SiH₂(OH), —Si(R₁)₂(OH),        —SiH(OH)₂, —SiR₁(OH)₂, —Si(OH)₃, —Si(OR₁)₃, —(SiR₁R₂O)_(x)—R₃,        —Si(R₃)₃, (X)_(m), where X is a halogen, x is the number of        repetitive units between 1 to 500, m is the number of        replacement groups, and can vary from 0 to 3, R₁ and R₂ are        identical or different, and can be alkoxy or alkyl groups,        linear or branched, cycloalkyl, aryl, alkylaryl, aralkyl or        vinyl, in each case having from 1 to 20 carbon atoms, and R₃ is        H or alkyl, branched or linear, in each case having from 1 to 20        carbon atoms, or a mononuclear aryl group; and    -   Siloxane groups that contain amine groups, represented by the        formula        —A¹-Si(A²-N((H)_(k)(R₁)_(2-k)))_(y)(OR₁)_(z)(R₃)_(3-(y+z), where: k can vary from)        0 to 2, y can vary from 1 to 3, z can vary from 0 to 2, 0≦y+z≦3,        being that, R₁ and R₂ are identical or different, and can be        alkyl groups, linear or branched, cycloalkyl, aryl, alkylaryl,        aralkyl or vinyl, in each case having from 1 to 20 carbon atoms,        aryl mononuclear groups, R₃ is H or alkyl, branched or linear,        in each case having from 1 to 20 carbon atoms, or a mononuclear        aryl group, and A¹ and A² are chains of up to 12 carbon atoms,        linear or branched, preferentially alkyl, alyl or vinyl.

For the elastomers of this invention, preferential use is given tohexamethylcyclotrisiloxane (D₃), which allows the terminal incorporationof the continuous sequences of the functional group —[—Si(CH₃)₂—O—]—,with different lengths, and a silanol terminal group —Si(CH₃)₂—OH.

As previously stated, these elastomers are obtained by the process ofanionic polymerization in solution. The utilization of thispolymerization process requires that all the materials employed are voidof any impurities that may in any way prejudice the end result of thepolymerization, such as humidity, chain transfer agents, etc.

This invention uses a method of polymerization divided into sequentialsteps, which allows a large control over the polymeric architecture.

In the first step, the random copolymerization of main chain isperformed, in an appropriate reactor, involving the selected monomers.Normally a monomer with an aromatic vinyl structure (e.g.: styrene) anda conjugated diene (e.g.: 1,3-butadiene) are employed in the appropriateproportions. The percentage ratio in weight between these monomersvaries in the range from 5% to 50% for the aromatic vinyl monomer andfrom 50% to 95% for the conjugated diene. More specifically, it adopts achemical content in the range from 15% to 40% in weight for the aromaticvinyl monomer, and in the range from 60% to 85% in weight for theconjugated diene, for these copolymers.

The copolymerization reaction is conducted in an appropriate apolarsolvent, normally using cyclohexane or n-hexane.

The percentage ratio in weight monomers/solvent is controlled to ensurethat the chemical content of the total solids at the end of the reactionare found in the range from 8% to 30%. More specifically, it is employedin the range of total solids employed is in the range of from 10% to18%, and even more specifically, it is desirable that the chemicalcontent of the solids of these reactions is between 12% to 16%.

For the initiation of these reactions, organometallic compounds oflithium are employed. N-butyl-lithium is preferred as the initiator, dueto its appropriate reactivity with the copolymerization1,3-butadiene-styrene and its larger commercial availability.

The quantity employed of this initiator is related to the total mass ofthe monomers employed in the reaction and the end molecular weightdesired for the copolymer.

A polar additive is also used at this step of the copolymerization,which acts as a Lewis base, which is added to the rectional medium,before the start of the reaction. Its function is to increase thechemical content of the 1,2-vinylic units of the polymeric chains.

These copolymers present a chemical content of 1,2-vinylic units in therange from 8% to 80%, considering the total of the diene incorporatedwith the copolymer.

It is desirable that the chemical content of the 1,2-vinylic units be inthe range from 10% to 70%. More specifically, a chemical content of1,2-vinylic units between 55% and 65% is preferred.

This additive is not consumed during the copolymerization and thequantity utilized depends on an appropriate molar relation with thequantity of initiator employed. This relation is chosen to allow abetter control of the kinetics of the reaction, as well as themicrostructure of the diene incorporated with the copolymer.

The reaction of the copolymerization, strictly speaking, is achieved inthe range of temperature between 35° C. and 120° C. More specifically,the copolymerization is achieved between 40° C. and 90° C. Even morespecifically, the copolymerization is achieved between 50° C. and 80°C., which is maintained until the total conversion of the monomers,which normally occurs between 30 and 45 minutes. The control of thetemperature during this step is fundamental for the obtainment of thedesired chemical content of the 1,2-vinylic units, which vary dependingon the temperature of the reaction.

The pressure of the reactor during this step varies normally in therange from 2 Kgf/cm² to 6 Kgf/cm².

Once the total conversion of the comonomers is achieved in the firststep, in a second step a determinate quantity of monomer(s) are addedthat will compose the small end block of the main polymeric chains.

This addition is performed over the active anionic chains of thecopolymer, in the range of temperature between 55° C. and 90° C. Morespecifically, it occurs in the range of temperature between 60° C. and75° C., with the reactor pressure in the range from 2 Kgf/cm² to 6Kgf/cm².

The rectional medium is maintained in these conditions until the totalconversion of the added monomer(s), which normally occurs between 10 and20 minutes.

Once the total conversion of the monomer(s) is achieved, in a thirdstep, the compound is added that will functionalize the copolymer withthe still active anionic chains, which now incorporate a small end blockwith a structure differentiated from the main chain, in the range oftemperature between 60° C. and 80° C., and the same range of pressureemployed in the previous step.

Preferentially, hexamethylcyclotrisiloxane (D₃) is employed as thefunctionalizing agent. This cyclic compound allows, by the opening ofits ring, the incorporation of the continuous sequences of the siloxanefunctional group (—[—Si(CH₃)₂—O—]—).

Once this step is concluded, which normally takes from 15 to 20 minutes,a terminator agent is added, maintaining the same previous reactionaryconditions. Cetylic alcohol, or other alcohol with a high molecularweight, is employed as the terminator agent of the polymerization.

This final step is normally concluded in 10 minutes, with thedeactivation of all the active anionic chains and the formation of thesilanol terminal group —Si(CH₃)₂—OH in the polymeric chains.

The resulting elastomer, still in solution, is subsequently stabilizedwith the addition of an appropriate quantity of trynonylphenylphosphiteand octadecyl 3,5-di-t-butyl-4-hydroxyhydrocinnamate antioxidants.

EXAMPLES

Illustrative examples of the invention now follow. However, theseexamples do not, in any manner or form, limit the scope of this claim.

Example 1 (B2)

Preparation of an elastomer of type s-SBR functionalized, whose mainpolymeric chains have a random distribution in their constituent mersand a controlled microstructure, containing an end block ofpolybutadiene, followed by a continuous sequence of the siloxanefunctional group (—[—Si(CH₃)₂—O—]—) and a silanol termination(—Si(CH₃)₂—OH).

A schematic representation of the structure of this elastomer ispresented below:

where, R₁ and R₂═CH₃; PBD=block of polybutadiene; n=n° of siloxane units

In a 2 liter capacity reactor, equipped with a turbine type mechanicalagitator and a refrigeration cover, the first step was performed of theanionic copolymerization of the 1,3-butadiene monomers and styrene, in asolution of cyclohexane, with the polar additive TMEDA, and usingn-butyl-lithium as the initiator.

For this copolymerization, the reactor was filled with 182 g of1,3-butadiene, 46 g of styrene, 1290 g of cyclohexane and 1.5 g ofTMEDA, aiming for a chemical content of total solids at the end of thereaction of 15% in weight.

For the initiation, a quantity of 0.085 g of n-butyl-lithium was used,which was necessary to neutralize any impurities still present in thematerials being utilized and to initiate the copolymerization, strictlyspeaking. The copolymerization was conducted semi-adiabatically, withthe temperature between 60° C. and 70° C., until the total conversion ofthe monomers.

In a second step, 5.5 g of 1,3-butadiene was added to the reactor. Thismonomer reacts with the active anionic chains of the rectional medium,forming a small block of polybutadiene at the end of the chains. Thisstep of the polymerization of the 1,3-butadiene was accomplished withthe temperature between 60° C. and 75° C., until the total conversion ofthe monomer.

Subsequently, in a third step, 1.8 g of hexamethylcyclotrisiloxane (D₃)was added, which reacts with the active anionic terminals of thepolymeric chains, forming a sequence of siloxane functional groups. Thisthird step was conducted with the temperature between 60° C. and 70° C.,for a period of 15 to 20 minutes.

Finally, in the last step, 0.4 g of cetylic alcohol was added, todeactivate all the active anionic terminals, forming the silanolterminal group in the polymeric chains. This step took 10 minutes andwas conducted with the temperature between 60° C. and 70° C.

The elastomer obtained in this way, and still in solution, wassubsequently stabilized with the addition of 0.9 g of the antioxidanttrynonylphenylphosphite and 0.5 g of the antioxidant octadecyl3,5-di-t-butyl-4-hydroxyhydrocinnamate.

The produced elastomer was recovered by the drying by evaporation of thesolvent of the polymeric solution, in an open mill, heated to 100° C.

The Mooney viscosity (Ml1+4 @ 100° C.) of the produced elastomer was 58.The total chemical content of styrene in the copolymer was 19.6% and thechemical content of the 1,2-vinylic units, based on the incorporated1,3-butadiene, was 63.7%. Both these results were obtained using RMNspectroscopy.

The molecular weight and the polydispersion of the elastomer weredetermined by Size Exclusion Chromatography, based on the standards ofpolystyrene, providing the values Mw=430.000 g/mol; Mn-340.000 g/mol andpd=1.2 respectively.

With the values of the obtained molecular weights and the masses of theadded materials and the number of moles of the determined activeinitiator, it was possible to determine that the polymeric chains of theobtained elastomer in average had a block of polybutadiene ofapproximately 150 mers, on average.

The confirmation of the functionalization of the elastomer was obtainedvia RMN ¹H spectroscopy, analyzing a sample of the elastomer submittedto a process of purification, in which a cycle of dissolution incyclohexane followed by coagulation in ethanol and drying, was repeated3 times, to remove any residual of the functionalizing agent notincorporated in the polymeric chains. The analysis was performed withthe sample dissolved in CDCl₃ (deuterated chloroform), without the useof TMS (tetramethylsilane) as a marker.

A spectrum of RMN ¹H characteristic of elastomer functionalized withsiloxane, presented typical signs or bands of the hydrogen element ofthe methyl groups linked to the silicon element, in the region between 0and 0.1 ppm.

The results of the RMN ¹H analyses, together with the results of theSize Exclusion Chromatography and the number of moles of the determinedactive initiator, allowed the obtainment of an average value for thelength of the sequences of the siloxane functional group(—[—Si(CH₃)₂—O—]—), including the silanol terminal group (—Si(CH₃)₂—OH),which were incorporated in the polymeric chains, which in this casecorresponded to 5 units.

In Table 3, the results of the characterization of this elastomer arepresented.

TABLE 3 Elastomer S-SBR Example 01 Mooney Viscosity 58.0 (Ml 1 + 4) at100° C. Total styrene content, 19.6 in copolymer, % weight, RMN¹HContent of 63.7 1,2-Vinylic Units, % ^((a)) Block with mers of butadieneat the Average of 150 mers end of the main chain per polymeric chainFunctionalization Average of 5 groups —[—Si(CH₃)₂—O—]_(n)—Si(CH₃)₂—OHper polymeric chain, including the silanol terminal group ^((a)) = basedon the content of the diene incorporated in the copolymer

Example 2 (C2)

Preparation of an elastomer of type s-SBR functionalized, whose mainpolymeric chains have random distribution in their constituent mers anda controlled microstructure, containing an end block of polystyrene,followed by a continuous sequence of the siloxane functional group(—[—Si(CH₃)₂—O—]—) and a silanol termination (—Si(CH₃)₂—OH).

A schematic representation of the structure of this elastomer ispresented below:

where, R₁ and R₂═CH₃; PS=block of polystyrene; n=n° of siloxane units

In a 2 liter capacity reactor, equipped with a turbine type mechanicalagitator and a refrigeration cover, the first step was performed of theanionic copolymerization of the 1,3-butadiene monomers and styrene, in asolution of cyclohexane, with the polar additive TMEDA, and usingn-butyl-lithium as the initiator.

For this copolymerization, the reactor was filled with 146 g of1,3-butadiene, 37 g of styrene, 1343 g of cyclohexane and 1.1 g ofTMEDA.

For the initiation, a quantity of 0.072 g of n-butyl-lithium was used,which was necessary to neutralize any impurities still present in thematerials being utilized and to initiate the copolymerization, strictlyspeaking. The copolymerization was conducted semi-adiabatically, withthe temperature between 50° C. and 70° C., until the total conversion ofthe monomers.

In a second step, 9.3 g of styrene was added to the reactor. Thismonomer reacts with the active anionic chains of the rectional medium,forming a small block of polystyrene at the end of the chains. This stepof the polymerization of the styrene was accomplished with thetemperature between 70° C. and 80° C., until the total conversion of themonomer.

Subsequently, in a third step, 0.3 g of hexamethylcyclotrisiloxane (D₃)was added, which reacts with the active anionic terminals of thepolymeric chains, forming a sequence of siloxane functional groups. Thisthird step was conducted with the temperature between 70° C. and 80° C.,for a period of 15 to 20 minutes.

Finally, in the last step, 0.3 g of cetylic alcohol was added, todeactivate all the active anionic terminals, forming the silanolterminal group in the polymeric chains. This step took 10 minutes andwas conducted with the temperature between 70° C. and 80° C.

The elastomer obtained in this way, and still in solution, wassubsequently stabilized with the addition of 0.7 g of the antioxidanttrynonylphenylphosphite and 0.4 g of the antioxidant octadecyl3,5-di-t-butyl-4-hydroxyhydrocinnamate.

The produced elastomer was recovered by the drying by evaporation of thesolvent of the polymeric solution, in an open mill, heated to 100° C.

The Mooney viscosity (Ml1+4 @ 100° C.) of the thus produced elastomerwas 55. The total chemical content of styrene in the copolymer was 23.3%and the chemical content of the 1,2-vinylic units, based on theincorporated 1,3-butadiene, was 61.0%. Both these results were obtainedusing RMN ¹H spectroscopy.

The molecular weight and the polydispersion of the elastomer weredetermined by Size Exclusion Chromatography, based on the standards ofpolystyrene, providing the values Mw=358.000 g/mol; Mn=260.000 g/mol andpd=1.3 respectively.

To obtain the characterization results of this elastomer, the sameprocedures and analytical methods used in example 1 were adopted.

In Table 4, the results of the characterization of this elastomer arepresented.

TABLE 4 Elastomer S-SBR Example 02 Mooney Viscosity 55 (Ml 1 + 4) at100° C. Total styrene content, 23.3 in copolymer, % of weight, RMN¹HContent of 61.0 1,2-Vinylic Units, % ^((a)) Block with mers of styreneat the end of Average of 130 mers the main chain per polymeric chainFunctionalization Average of 3 groups —[—Si(CH₃)₂—O—]_(n)—Si(CH₃)₂—OHper polymeric chain, including the silanol terminal group ^((a)) = basedon the content of the diene incorporated in the copolymerPreparation of the Vulcanized Compounds and their Properties.

For a better evaluation of the properties of these elastomers, it isnecessary to test them in the vulcanized compounds employed in theproduction of tires.

The preparation of these compounds follows conventional methods. Thedifferent components are mixed in distinct steps, in the appropriateequipment, followed by the final step of vulcanization, where thecrossed links connections occur that provide the final form.

Contained in the recipe of the preparation of these compounds, as wellas the elastomers to be tested, are other elastomers such as naturalrubber (NR) and polybutadiene (BR). There are also other importantcomponents, such as the fillers, among them silica, oils, accelerators,antiozonants, antioxidants, stearic acid, plasticizers, etc, as well asthe vulcanization system, consisting basically of sulfur or compoundsthat produce sulfur during the vulcanization step.

To compare the results, a vulcanized compound was prepared, using areference elastomer.

The materials used in the preparation of the vulcanized compoundscontaining the elastomers of this invention and the reference compound,are presented in Tables 6 and 9.

The vulcanized compounds were prepared in the following manner:

In the first step, all the components were mixed in a laboratorytangential mixer, except those pertaining to the system ofvulcanization. Once the pre-mixture was obtained, the vulcanizationsystem components were added. The final mixture, containing all therequired components, was then processed in an extruder and convertedinto the pre-form of a tread, used for the production of tires.

After the vulcanization in high pressures and temperatures, trialsamples were prepared to be subsequently tested to determine the typicalproperties of the vulcanized compounds. The results are used as thefinal performance indicators of these materials.

The following test methods were employed to evaluate the properties ofthe compounds:

-   -   Hardness Shore A, in an ambient temperature and at 70° C. norm        DIN 53 505;    -   Rebound resilience, at an ambient temperature and at 70° C.,        norm DIN 53 512;    -   Tensile strength, at an ambient temperature, norm DIN 53 504;    -   Elongation at break, at an ambient temperature, norm DIN 53 504;    -   Stress modulus at 100% and at 300% of elongation, at an ambient        temperature, norm DIN 53 504;    -   Tan delta at 0° C. measured using a dynamic deformation with an        amplitude of 0.2%, with 10% pre-deformation, at a frequency of        10 Hz;    -   Storage modulus average E′, with the temperature from −25° C. to        −5° C., norm DIN 53 513, using a deformation with an amplitude        of 0.2%, with 10% pre-deformation, at a frequency of 10 Hz;

Example 3

Vulcanized elastomeric compounds prepared with the group 1 elastomers.

The group 1 elastomers are type S-SBR. Their main polymeric chains havea random distribution in their constituent mers and a controlledmicrostructure, containing an end block of polybutadiene, followed by acontinuous sequence of the siloxane functional group (—[—Si(CH₃)₂—O—]—)and a silanol termination (—Si(CH₃)₂—OH).

In Table 5, the main characteristics of these elastomers are presented.

TABLE 5 S-SBR Block of Terminal Elastomer composition polybutadieneFunctionalization A₂ 21.0% styrene; not present siloxane groups and(reference) 63.0% 1,2- terminal silanol vinyl ^((a)) B₁ 19.0% styrene;Block with an siloxane with an average 64.1% 1,2- average of 50 of 8.0groups per chain vinyl ^((a)) mers of including silanol terminalbutadiene group per chain B₂ 19.6% styrene; Block with an siloxane withan average 63.7% 1,2- average of 150 of 5.0 groups per chain vinyl^((a)) mers of including silanol terminal butadiene group per chain^((a)) = based on the content of the diene incorporated in the copolymerwhere, A₂ is the elastomer used as the reference in the comparativetests, which has a composition similar to the elastomers B₁ and B₂.However, it does not have a block of polybutadiene at the end of thepolymeric chains, and is functionalized with the terminal siloxane andsilanol groups, as described in patent EP 110998.

The elastomers B₁ and B₂ were prepared as described in example 1, withadjustments made to the quantities of the employed materials, asrequired.

The recipe used for the preparation of the vulcanized compounds, usingthe elastomers A₂, B₁ and B₂, is presented in Table 6.

The relative quantities of the components are expressed as a percentageof rubber, or pcb.

TABLE 6 Components, Vulcanized compounds pcb A₂ B₁ B₂ A₂-BR B₁-BR B₂-BRA₂ (reference) 100 — — 50 — — B₂ — — 100 — — 50 B₁ — 100 — — 50 — BR — —— 50 50 50 Silica 95 95 95 95 95 95 Oil 35 35 35 45 45 45 6PPD 2 2 2 2 22 TMQ 2 2 2 2 2 2 Antiozonant 2 2 2 2 2 2 (wax) ZnO 2.5 2.5 2.5 2.5 2.52.5 Stearic acid 2.5 2.5 2.5 2.5 2.5 2.5 Silanol 8.075 8.075 8.075 6.6506.650 6.650 DPG 2 2 2 2 2 2 CBS 2 2 2 1.6 1.6 1.6 Sulfur 2 2 2 2 2 2Where: BR = polybutadiene rubber; 6PPD =N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine; TMQ =2,2,4-trimethyl-1,2-dihydroquinoline DPG = N,N-diphenylguanidine CBS =benzotriazol-2-cyclohexylsulfenamide; Oil = type TDAE (Treated andDistilled Aromatic Extract); Silica = VN3, Degussa AG, Germany, surfacearea: 175 m²/g, CTAB 160 m²/g; Silanol (functionalization reagent) =SILQUEST A 1589, General Electric, USA.

In Table 7, the results obtained in the abovementioned tests for thedifferent prepared compounds, are presented.

TABLE 7 Vulcanized compounds Measured property A₂ B₁ B₂ A₂-BR B₁-BRB₂-BR Hardness 68.3 69.8 70.7 62.8 63.6 63.1 Shore A at an ambienttemperature Hardness 65.0 66.6 67.6 59.0 59.9 59.3 Shore A, 70° C.Rebound resilience, % 15.0 14.9 14.5 32.2 32.4 32.7 at an ambienttemperature Rebound resilience, % 50.4 48.9 48.9 46.9 44.9 45.5 at 70°C. Tensile Strength, 14.8 14.7 13.1 14.8 14.1 14.3 Mpa at an ambienttemperature Elongation at break, % 325 340 309 578 577 576 at an ambienttemperature Stress, Mpa 3.18 3.26 3.26 1.66 1.79 1.78 at 100%deformation Stress, Mpa 14.97 13.96 14.46 6.30 6.22 6.29 at 300% ofdeformation E′, Mpa 630 451 449 35 32 33 with the temperature between(−25° C. to −5° C.)

The measurement of the storage modulus E′, with the temperature between−25° C. to −5° C., can be considered as a performance indicator for icyskid resistance. A reduction in the values of E′ indicates animprovement in this property.

In Table 7, it can be observed that both the vulcanized compounds B₁ andB₂, compared to the reference compound A₂, and the vulcanized compoundsB₁-BR and B₂, BR, compared to the reference compound A₂-BR, presentlower values for the storage modulus E′, indicating a significantimprovement in icy skid resistance.

The rebound resilience at the ambient temperature can be used as anindicator for wet skid resistance, where lower values indicate animprovement in this property.

The comparison of the results obtained for this property, between theaforementioned compounds and their respective references, indicates thatthey remain practically unaltered, and that the performance of thesecompounds, in relation to wet skid resistance, was maintained.

The elastomers of this invention, which have main polymeric chains witha random distribution in their constituent mers and a controlledmicrostructure, containing an end block of polybutadiene, followed by acontinuous sequence of the siloxane functional group (—[—Si(CH₃)₂—O—]—)and a silanol termination (—Si(CH₃)₂—OH), make possible the obtainmentof elastomeric vulcanized compounds, which have the advantage ofpresenting a significant improvement in the icy skid resistance, withoutprejudicing the wet skid resistance. Both these properties are desirablein high performance tires.

Example 4

Vulcanized elastomeric compounds prepared with the group 2 elastomers.

The group 2 elastomers are type S-SBR. Their main polymeric chains havea random distribution in their constituent mers and a controlledmicrostructure, containing an end block of polystyrene, followed by acontinuous sequence of the siloxane functional group (—[—Si(CH₃)₂—O—]—)and a silanol termination (—Si(CH₃)₂—OH).

In Table 8, the characteristics of these elastomers are presented.

TABLE 8 SSBR Block of Terminal Elastomer composition polystyrenefunctionalization A₁ 21.0% styrene; not present Amine terminal groups(reference) 63.0% 1,2- vinyl ^((a)) C₁ 21.4% styrene; Block with ansiloxane with an average 62.8% 1,2- average of 54 of 3.0 groups perchain vinyl ^((a)) mers of styrene including silanol terminal per chaingroup C₂ 23.3% styrene Block with an siloxane with an average 61.0% 1,2-average of 130 of 3.0 groups per chain vinyl ^((a)) mers of styreneincluding silanol terminal per chain group ^((a)) = based on the contentof the diene incorporated in the copolymer where, A₁ is the elastomerused as the reference in the comparative tests, which has a compositionsimilar to the elastomers C₁ and C₂. However, it does not have a blockof polystyrene at the end of the polymeric chains, and is functionalizedterminally with the amine groups.

The elastomers C₁ and C₂ were prepared as described in example 2, withadjustments made to the quantities of the employed materials, asrequired.

The recipe used for the preparation of the vulcanized compounds, usingthe elastomers A₁, C₁ and C₂, is presented in Table 9.

The relative quantities of the components of the recipe are expressed asa percentage of rubber, or pcb.

TABLE 9 Components, Vulcanized compounds pcb A₁ C₁ C₂ C₁-NR C₂-NR C₁-BRC₂-BR NR — — — 50 50 — — BR — — — — — 50 50 A₁ (ref.) 100 — — — — — — C₁— 100 — 50 — 50 — C₂ — — 100 — 50 — 50 Silica 95 95 95 95 95 95 95 Oil35 35 35 35 35 35 35 6PPD 2 2 2 2 2 2 2 TMQ 2 2 2 2 2 2 2 Antiozonant 22 2 2 2 2 2 (Wax) ZnO 2 2 2 3 3 3 3 Stearic Acid 2 2 2 3 3 3 3 Silanol 98 8 8 8 8 8 DPG 2 2 2 2 2 2 2 CBS 2 2 2 2 2 2 2 Sulfur 2 2 2 2 2 2 2Where: NR = natural rubber; BR = polybutadiene rubber; 6PPD =N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine; TMQ =2,2,4-trimethyl-1,2-dihydroquinoline; DPG = N,N-diphenylguanidine; CBS =benzotriazol-2-cyclohexylsulfenamide; Oil = type TDAE (Treated andDistilled Aromatic Extract); Silanol = functionalization reagentSILQUEST A-1589, General Electric, USA. Silica = VN3, Degussa AG,Germany, surface area: 175 m²/g, CTAB 160 m²/g;

In Table 10, the results obtained in the abovementioned tests for thedifferent prepared compounds, are presented.

TABLE 10 Measured Vulcanized compounds property A₁ C₁ C₂ C₁-NR C₂-NRC₁-BR C₂-BR Hardness 75.3 73.5 76.5 72.8 72.5 72.1 71.8 Shore A at anambient temperature Hardness 70.4 70.5 70.0 69.2 67.9 69.3 68.1 Shore A,70° C. Rebound 15.6 14.9 13.3 22.0 19.3 32.2 28.6 resilience, % at anambient temperature tan delta 0.540 0.554 0.576 0.365 0.384 0.276 0.289at 0° C. Stress, Mpa 3.60 3.50 3.62 2.49 2.37 2.61 2.47 at 100%deformation Rebound 42.5 44.4 37.0 44.9 40.9 47.7 43.9 resilience, % at70° C.

The measurement of rebound resilience to the ambient temperature and thetan delta at 0° C., are conventional indicators of wet skid resistance.There is always an improvement in the performance of this property whenthe values for the rebound resilience to ambient temperature reduce andthe values for the tan delta at 0° C. increase.

The results presented in Table 10 indicate an improvement in thisproperty, for the vulcanized compounds C₁ and C₂, when compared with thereference compound A₁, since both C₁ and C₂ have reduced reboundresiliencies to the ambient temperature, and an increase in the valuesof the tan delta at 0° C.

The combination of the measurements of rebound resilience at 70° C. andof stress at 100% deformation is used for an evaluation of the handlingperformance of a tire. The decrease in the values of the reboundresilience at 70° C. indicates an improvement in the handlingperformance of the tire, as does an increase in the values of stress at100% deformation.

From a comparison between the results of the vulcanized compounds C₁ andC₂ in relation to the reference compound A₁, it can be seen that thevalues of the rebound resilience at 70° C., and the stress at 100%deformation, only present discrete variations, indicating that thehandling performance remains unaltered.

The elastomers of this invention, which have main polymeric chains witha random distribution in their constituent mers and a controlledmicrostructure, containing an end block of polystyrene, followed by acontinuous sequence of the siloxane functional group (—[—Si(CH₃)₂—O—]—)and a silanol termination (—Si(CH₃)₂—OH), make possible the obtainmentof elastomeric vulcanized compounds, which have the advantage ofcombining properties such as a good performance in wet skid resistance,without affecting the handling performance. These are desirableproperties in high performance tires.

This invention was described in terms of its preferred embodiment andthe examples were provided in a purely illustrative manner and shouldnot limit the scope of this document. In the same way, certainmodifications and/or alterations may become apparent to a person skilledin the art, arising from this specification. However, any suchmodifications and/or alterations are deemed to be included in the scopeof this present invention.

1. A process for preparing copolymer of 1,3-butadiene and styrene containing in its main chain a random segment, followed by a block having a different structure to the main chain, homopolymeric or copolymeric, functionalized and characterized by comprising the steps of: a first step of random copolymerization corresponding to an aromatic vinyl structure monomer and a conjugated diene with percentage relationship ranging between monomers of 5% to 50% w/w, for the aromatic vinyl monomer, and ranging from 50% to 95% w/w for the conjugated diene; a second step of adding a determined quantity of the monomer(s) in a temperature range of between 55° C. and 90° C., with the reactor pressure ranging from 2 Kgf/cm² to 6 Kgf/cm²; a third step of adding functionalization compound of the copolymer in a temperature range of between 60° C. and 80° C., in the same pressure range as used in the prior step; and a stabilization step comprising the addition of antioxidants trinonylphenylphosphite and octadecyl 3,5-di-t-butyl-4-hydroxyhydrocinnamate.
 2. The process of claim 1, characterized by the fact that in the copolymerization step the percentage relationship between these monomers varies from 15% to 40% w/w for the aromatic vinyl monomer and from 60% to 85% w/w for the conjugated diene.
 3. The process of claim 1, characterized by the fact that the solvent employed in the copolymerization step belongs to the class of aliphatics, is preferably one of among cyclohexane and n-hexane.
 4. The process of claim 1, characterized by the fact that in the copolymerization step the percentage relationship w/w monomers/solvent corresponds to a content of solids between 8% and 30% w/w.
 5. The process of claim 4, characterized by the fact that the content of solids is comprised between 10% and 18% w/w.
 6. The process of claims 4 and 5, characterized by the fact that the content of solids is comprised between 12% and 16% w/w.
 7. The process of claim 1, characterized by the fact that the copolymerization step employs an organometallic initiator of lithium which comprises at least one of among methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, n-amyl, sec-amyl, n-hexyl, sec-hexyl, n-heptyl, n-octyl, n-nonyl, n-dodecyl, octadecyl and isobutyl-lithium.
 8. The process of claim 1, characterized by the fact that in the copolymerization step the content of 1,2-vinylic units varies between 8% and 80% in relation to the conjugated diene incorporated in the polymer.
 9. The process of claim 8, characterized by the fact that the content of 1,2-vinylic units varies between 10% and 70%, in relation to the conjugated diene incorporated in the polymer.
 10. The process of claim 8, characterized by the fact that the content of 1,2-vinylic units varies between 55% and 65%, in relation to the conjugated diene incorporated in the polymer.
 11. The process of claim 1, characterized by the fact that the copolymerization step occurs at a temperature between 35° C. and 120° C.
 12. The process of claim 11, characterized by the fact that the copolymerization step occurs at a temperature between 40° C. and 90° C.
 13. The process of claim 11, characterized by the fact that the copolymerization step occurs at a temperature between 50° C. and 80° C.
 14. The process of claim 1, characterized by the fact that the monomer(s) addition step that will comprise the block having a different structure to the main chain occurs at a temperature between 55° C. and 90° C.
 15. The process of claim 14, characterized by the fact that the monomer(s) addition step that will comprise the block having a different structure to the main chain occurs at a temperature between 60° C. and 75° C.
 16. The process of claim 1, characterized by the fact that the reaction time of the block formation step having a different structure from the main chain varies between 10 and 20 minutes.
 17. The process of claim 1, characterized by the fact that the elastomer functionalization step occurs at a temperature between 60° C. and 80° C.
 18. The process of claim 1, characterized by the fact that the elastomer functionalization step occurs in a reaction time varying between 15 and 20 minutes.
 19. The process of claim 1, characterized by the fact that the functionalization step employs hexamethylcyclotrissiloxane (D₃) and a terminator agent chosen from cetylic alcohol or a high molecular weight alcohol.
 20. The process of claim 1, characterized by the fact that in the functionalization step, the termination reaction occurs at a time of around 10 minutes.
 21. Copolymer product of 1,3-butadiene and styrene containing in its main chain a random segment, followed by a block having a different structure to the functionalized main chain, homopolymeric or copolymeric, characterized by comprising the following structure:

wherein, A represents the main chains of a polymer, formed by the copolymerization between one or more conjugated dienes with one or more monomers having aromatic vinyl structure, which have a preferably random distribution of their constituent mers, linear or branched structure, and a controlled content of 1,2-vinylic units, based on the conjugated diene incorporated; B represents a block having a different structure from the main chain, homopolymeric or copolymeric, or else, copolymerization of two or more monomers with aromatic vinyl structure, or else, copolymerization of one or more conjugated dienes with one or more monomers having aromatic vinyl structure, including the different possible microstructures for the diene(s) employed, provided that the final structure of this block is different from the main chain; and F is a terminal functional group of polymeric chains of the —OH, —COOH, —COX type, wherein X is a halogen, —SH, —CSSH, —NCO, amine, epoxy, silyl, silanol or siloxane, in addition to polysiloxane and siloxane or polysiloxane groups containing amine groups, preferably being: Amine groups: —N(R₁)₂, NR1R2, —NHR₁, —NH₂, wherein R₁ and R₂ are identical or different, may be alkyl, linear or branched, cycloalkyl, aryl, alkylaryl, aralkyl or vinyl groups, in each case having from 1 to 20 carbon atoms; Silyl, silanol and siloxane groups: —SiH₂(OH), —Si(R₁)₂(OH), —SiH(OH)₂, —SiR₁(OH)₂, —Si(OH)₃, —Si(OR₁)₃, —(SiR₁R₂O)_(x)—R₃, —Si(R₃)_(3-m)(X)_(m), wherein X is a halogen, x is the number of repetitive units between 1 and 500, m is the number of ligant groups, varying from 0 to 3, R₁ and R₂ are identical or different, and may be alkoxy or alkyl, linear or branched, cycloalkyl, aryl, alkylaryl, aralkyl or vinyl groups, in each case having from 1 to 20 carbon atoms, and R₃ is H or alkyl, branched or linear, in each case having from 1 to 20 carbon atoms, or a mononuclear aryl group; Siloxane groups that contain amine groups, represented by the formula -A¹-Si(A²—N((H)_(k)(R₁)_(2-k)))_(y)(OR₁)_(Z)(R₃)_(3-(y+z)), wherein: k may vary from 0 to 2, y may vary from 1 to 3, and z may vary from 0 to 2 and 0≦y+z≦3, wherein, R₁ and R₂ are identical or different, and may be alkyl, linear or branched, cycloalkyl, aryl, alkylaryl, aralkyl or vinyl groups, in each case having from 1 to 20 carbon atoms, mononuclear aryl groups, R₃ is H or alkyl, branched or linear, in each case having from 1 to 20 carbon atoms, or a mononuclear aryl group, and A¹ and A² are chains of up to 12 carbon atoms, branched or linear, preferably alkyl, alyl or vinyl.
 22. A copolymer product of 1,3-butadiene and styrene of claim 21, characterized by the fact that it comprises the following structure:

wherein S-SBR represents a copolymer chain of 1,3-butadiene-styrene; R₁ and R₂═CH₃; PBD=block of polybutadiene in which the number of mers varies from 5 to 250 units; preferably between 10 and 200 units and more preferably between 20 and 180 units, n=number of siloxane units, varying between 1 and
 500. 23. The copolymer product of 1,3-butadiene and styrene of claim 21, characterized by the fact that it comprises the following structure:

wherein, S-SBR represents a copolymer chain 1,3-butadiene-styrene; R₁ and R₂═CH₃; PS=block of polystyrene in which the number of mers varies from 5 to 250; preferably between 10 and 200 units and more preferably between 20 and 180 units, n=number of siloxane units, varying from 1 to
 500. 24. The copolymer product of 1,3-butadiene and styrene of claim 21, characterized by the fact that it comprises one or more conjugated dienes with one or more monomers having aromatic vinyl structure in which the conjugated dienes are selected from 1,3-butadiene, 2-alkyl-1,3-butadiene, 2,3-dialkyl-1,3-butadiene, 2-alkyl-3-alkyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene and the aromatic vinyl monomers are selected from styrene, alfa-methyl-styrene, orto, meta and para divinylbenzene, orto, meta and para-methylstyrene, para-t-butyl-styrene, vinyl-toluene, metoxystyrene, vinylmesitylene, among others.
 25. The copolymer product of 1,3-butadiene and styrene of claim 21, characterized by the fact that it comprises a content of 1,2-vinylic units between 8% and 80%, based on the total of conjugated diene incorporated in the copolymer.
 26. The copolymer product of 1,3-butadiene and styrene of claim 25, characterized by the fact that it comprises small polymeric blocks having a differentiated structure, located at the end of the polymeric chains whose length varies between 5 and 250 mers.
 27. The copolymer product of 1,3-butadiene and styrene of claim 26, characterized by comprising a length of polymeric blocks between 20 and 180 mers.
 28. The copolymer product of 1,3-butadiene and styrene of claim 21, characterized by the fact that the terminal functional group F of the polymeric chains are of the —OH, —COOH, —COX type, wherein X is a halogen, —SH, —CSSH, —NCO, amine, epoxy, silyl, silanol or siloxane, in addition to polysiloxane and siloxane or polysiloxane groups containing amine groups, preferably being: Amine groups: —N(R₁)₂, —NR1R2, —NHR₁, —NH₂, wherein R₁ and R₂ are identical or different, may be alkyl, linear or branched, cycloalkyl, aryl, alkylaryl, aralkyl or vinyl groups, in each case having from 1 to 20 carbon atoms; Silyl, silanol and siloxane groups: —SiH₂(OH), —Si(R₁)₂(OH), —SiH(OH)₂, —SiR₁(OH)₂, —Si(OH)₃, —Si(OR₁)₃, —(SiR₁R₂O)_(x)—R₃, —Si(R₃)_(3m)(X)_(m), wherein X is a halogen, x is the number of repetitive units between 1 and 500, m is the number of ligant groups, varying between 0 and 3, R₁ and R₂ are identical or different, and may be alkoxy or alkyl, linear or branched, cycloalkyl, aryl, alkylaryl, aralkyl or vinyl groups, in each case having from 1 to 20 carbon atoms, and R₃ is H or alkyl, branched or linear, in each case having from 1 to 20 carbon atoms, or a mononuclear aryl group; and Siloxane groups that contain amine groups, represented by the formula -A¹—Si(A²-N((H)_(k)(R₁)_(2-k)))_(y)(OR₁)_(z)(R₃)_(3-(y+z)), wherein: k may vary from 0 to 2, y may vary from 1 to 3, and z may vary from 0 to 2 and 0≦y+z≦3, wherein, R₁ and R₂ are identical or different, and may be alkyl, linear or branched, cycloalkyl, aryl, alkylaril, aralkyl or vinyl groups, in each case having from 1 to 20 carbon atoms, mononuclear aryl groups, R₃ is H or alkyl, branched or linear, in each case having from 1 to 20 carbon atoms, or a mononuclear aryl group, and A¹ and A² are chains of up to 12 carbon atoms, branched or linear, preferably alkyl, alyl or vinyl.
 29. The copolymer product of 1,3-butadiene and styrene of claim 21, characterized by the fact that terminal function groups of the polymeric chains selected from —[—Si(R₁R₂)—O—]_(n)—Si(R₁R₂)—OH, wherein R₁ and R₂ are identical or different, and may be alcoxy or alkyl, linear or branched, cycloalkyl, aryl, alkylaryl, aralkyl or vinyl groups, in each case having from 1 to 20 carbon atoms, and n represents the number of units of the functional siloxane group before a terminal silanol group.
 30. The copolymer product of 1,3-butadiene and styrene of claim 21, characterized by the fact that the elastomer presents a w/w percentage composition in its main chain that may respectively vary from 5% to 50%, for the aromatic vinyl monomer and from 50% to 95% for the conjugated diene.
 31. The copolymer product of 1,3-butadiene and styrene of claim 30, characterized by the fact that the elastomer respectively presents a composition ranging from 15% to 40%, in relation to the w/w percentage of the monomer with aromatic vinyl structure and from 60% to 85% in relation to the w/w percentage of the conjugated diene incorporated in the copolymer.
 32. The copolymer product of 1,3-butadiene and styrene of claim 21, characterized by the fact that the elastomer has a Mooney viscosity ranging from 30 to 90, and an average molecular weight ranging from 80,000 to 700,000, with a polydispersion ranging from 1.05 to 4.0.
 33. The copolymer product of 1,3-butadiene and styrene of claim 21, characterized by the fact that the elastomer presents glass transition temperatures, Tg, ranging from −92° C. to −1° C., preferably between −50° C. and 0° C. 